The present invention relates to a liquid crystal display element which is designed to provide a colored display by applying a voltage to a twisted type liquid crystal cell which contains liquid crystal and an N type dichroic dye and in which the orientation of molecules of the liquid crystal on one of opposite side plates of the cell is substantially perpendicular to the orientation of the molecules on the other side plate and molecules of the dye have the same orientation as the molecules of the liquid crystal.
Heretofore, there has been proposed a positive type color liquid crystal display element which contains in a liquid crystal cell an N type dye together with a nematic liquid crystal of positive dielectric anisotropy, and a pattern provided on an electrode is displayed by the application of a voltage to the liquid crystal cell. With this conventional liquid crystal display element, when incident light on one side plate of the liquid crystal cell is linearly polarized light whose plane of polarization is the same as the direction of the long axes of molecules of the liquid crystal near the abovesaid side plate of the liquid cell, the display element appears colorless on the side of the other side plate. In such a state, if a voltage is applied to the liquid crystal cell, the direction of the long axes of the molecules of the liquid crystal and the dye becomes perpendicular to the side plate of the cell and components of a certain wavelength in the incident light are absorbed by the molecules of the dye, making the display element appear to be colored. In this prior art liquid crystal display element, the color of the display is changed by selecting the dye which is mixed in the liquid crystal cell but, at present, the display is produced only in purple. Further, this display element has poor contrast because of the small difference between the transmissivity in the presence of an electric field produced by the application of a voltage to the liquid crystal cell and the transmissivity in the absence of such a field.
There has also been proposed a liquid crystal display element of the type that employs a cell containing nematic liquid crystal of positive dielectric anisotropy with no dye mixed therein and a color polarizing plate. In this display element, the direction of polarization of the color polarizing plate, which is disposed on the side of its display surface, is parallel to the direction of the long axes of molecules of the liquid crystal near the side plate of the cell which the color polarizing plate confronts. When no voltage is provided to the liquid crystal cell, light of all color components passes through the liquid crystal cell and the color polarizing plate, with the result that the display element appears to be colorless. When a voltage is applied to the liquid crystal cell, since the direction of polarization of light passing through the liquid crystal cell is not rotated, light of only the color component of the color polarizing plate passes therethrough, making the display element appear in the color of the color polarizing plate. This liquid crystal display element is capable of producing displays in various kinds of colors by selecting the color of the color polarizing plate and has relatively good contrast. Since this liquid crystal display element makes use of the polarizing characteristic of the color polarizing plate, however, in the angle over which the display can be seen correctly is small, that is, small in what is called the angle of visual field, and hence it has the defect that the display cannot be seen from an oblique direction, even if only slightly oblique.